Imported fire ants (FA) are a major economic and medical problem in the Southeastern United States. They are responsible for large numbers of both systemic and local hypersensitivity reactions, problems which can be expected to become worse with the continued spread of IFA. There is disagreement regarding the specific allergens causing hypersensitivity reactions to IFA. While IFA whole body extracts (IFWBE) have, in some cases, been reported to be useful for diagnosis and treatment of IFA hypersensitivity, the data are conflicting and some feel that use of IFA venom (IFAV) would be superior. A major problem has been the technical difficulty of obtaining sufficient IFAV for diagnostic studies and treatment. Our proposed studies will identify and characterize antigenic and allergenic components in IFWBE and IFAV using the highly specific new technology, crossed immunoelectrophoresis. Since the chemical structure of the major alkaloid component of IFAV is known, synthetic alkaloid will also be tested for its usefulness in immunologic studies of hypersensitivity to IFA. The specificity of blocking antibodies produced by individuals undergoing desensitization will also be evaluated using a novel approach which permits identification of the antigenic components of IFWBE. Furthermore, since reports of anaphylactic reactions occurring after the first IFA sting have raised the possibility of cross-reactivity between IFA and other Hymenoptera, venom from other stinging insects will be tested for cross-reactivity with IFAV and IFWBE. These studies will permit a better understanding of the nature of the allergens and, ultimately, the immunopathogenesis of hypersensitivity to IFA.